1. Technical Field of the Invention
The present invention relates to the field of electronics, and more particularly to a shared bicycle comprising an infrared sensor.
2. Prior Art
Shared bicycles have become a popular form of public transportation. They are intended to solve “the last kilometer” issue for commuters in which the destination is too far to walk, but too close to take a taxi. A shared bicycle comes with an electronic wheel lock and a GPS receiver. The electronic wheel lock automatically unlocks after receiving an unlock message, while the GPS receiver calculates the GPS coordinates of the bicycle from satellite signals. The shared bicycle also comprises communication electronics (e.g. a GSM module) for transferring the unlock message and the GPS coordinates with a remote server. The shared bicycle further comprises a battery. This battery is preferably rechargeable which could be powered by a solar panel mounted on the front basket or a generator installed on the rear wheel hub. During usage, a user opens a share-bicycle app on a cellular phone to locate a nearby bicycle and then scan its QR-code to open the electronic wheel lock. The emergence of shared bicycles reduces the number of taxi rides, lowers fuel consumption and has a positive impact to the environment.
A bicycle becomes an easy target for theft as it is much lighter than an electric motorcycle or an automobile. A thief would simply throw a locked bicycle into a carriage and transport it to a concealed place before disabling its wheel lock. To prevent theft like this, geo-fencing is an effective method. U.S. Pat. No. 9,194,955 issued to Fahrner et al. on Nov. 24, 2015 discloses a preferred geo-fencing method. In the geo-fencing mode, a locked bicycle continuously reports its GPS coordinates to a remote server. Once the reported GPS coordinates are outside the boundary of a pre-determined geo-fence, the bicycle is considered stolen and an alert message is sent. Because its GPS receiver and GSM module are both powered in the geo-fencing mode, even a locked bicycle would consume a fairly large current (˜60 mA, including ˜50 mA for the GPS receiver and ˜10 mA for the GSM module).
Due to the size and weight limits, the battery used by a shared bicycle has a much smaller capacity than those used by an electric motorcycle or an automobile. Accordingly, a shared bicycle has stringent requirements on power consumption. U.S. Pat. No. 5,945,794 issued to Kitamura on Aug. 31, 1999 teaches a power-saving control device for a bicycle. The bicycle comprises a lock control circuit and a magnetic sensor. A key associated with the bicycle includes a magnet. To save power, the lock control circuit is powered down when no magnet is detected. When the key is placed in such proximity to the bicycle that the magnetic sensor detects the magnet, the lock control circuit is powered and unlocks the bicycle. As few users are willing to carry a magnet to activate a bicycle, it would be difficult for Kitamura to gain wide acceptance.
The Mobike, a shared bicycle developed by a Chinese manufacturer, uses another power-saving method. Its electronics comprises a GSM module and a GPS receiver. Because it cannot be predicted when a locked bicycle will receive an unlock message, the GSM module is always in an idle mode (with a current drain of ˜7 mA) and ready to accept the unlock message. After a Mobike receives an unlock message and becomes unlocked, its GPS receiver calculates the GPS coordinates frequently (e.g. once every minute, with a substantial power drain), because the Mobike is assumed to be ridden around. To reduce the power consumption, once the Mobike is locked, its GPS receiver calculates the GPS coordinates much less frequently (e.g. once every ten minutes) or not at all (with a negligible power drain), because the Mobike is assumed to be stationary. Unfortunately, calculating the GPS coordinates infrequently or not at all would disable the anti-theft feature (e.g. the geo-fencing function) of a shared bicycle. Moreover, even though the power drain from the GPS receiver is reduced when the bicycle is locked, the GSM module still drains a substantial current. Further power saving is desired.